1. Field of the Invention
This invention relates to computer peripheral storage device backup systems, and more particularly to an automated concurrent data backup system and method.
2. Description of Related Art
It is common practice in the computer industry to provide a backup data storage device, such as a tape drive, for making a duplicate copy of data on one or more other storage devices, such as magnetic disk drives. Backup copies provide security in case of failure of the primary data storage device, and archive copies of data files for tracing previous generations of data.
As primary data storage devices increase in data storage capacity (for example, magnetic disk drives holding more than one gigabyte of data are currently available), the time required to make a complete backup of such devices has also increased. Some systems have grown to such a capacity that it takes more than a day to backup a day's worth of accumulated data. In some installations, backups are done overnight, or even over a weekend, simply in order to have enough time to make a complete backup copy of the data on the primary data storage devices.
In many areas of industry, it is important to have virtually daily backups of data. For example, in the hospital services field, it is important to have patient clinical and billing data backed up on a daily basis so that no more than a day's worth of data can be lost if a failure occurs in the primary data storage system.
In critical applications, computer systems often have multiple data storage devices coupled through a controller to a computer and operated in a "mirrored" or "shadowed" configuration. In a "mirrored" configuration, data storage devices are treated as pairs, and all data intended for a particular data storage device is duplicated on a block for block basis on the paired "mirror" data storage device. Shadowing is similar, except that logical blocks rather than physical blocks are duplicated on paired "shadow" drives. The principal purpose of mirroring or shadowing data storage devices is to be able to continue processing with the redundant data storage device if one of a mirrored pair of storage devices fails. Mirroring and/or shadowing can be accomplished by special circuitry or by computer program control, or by a combination thereof.
For a computer system having mirrored or shadowed primary data storage devices, it would be desirable to provide a means and method that could copy a primary data storage device to a backup data storage device without interrupting processing, or without requiring an extraordinary amount of time. It would also be desirable to provide such a means and method that did not require changes to the operating system of the computer.
The present invention provides such a means and method for computing systems having mirrored or shadowed primary data storage devices.